The conserved N-terminal BH4 domain of Bcl-2 homologues is essential for inhibition of apoptosis and interaction with CED-4.
Bcl-2 and close homologues such as Bcl-xL promote cell survival, while other relatives such as Bax antagonize this function. Since only the pro-survival family members possess a conserved N-terminal region denoted BH4, we have explored the role of this amphipathic helix for their survival function and for interactions with several agonists of apoptosis, including Bax and CED-4, an essential regulator in the nematode Caenorhabditis elegans. BH4 of Bcl-2 could be replaced by that of Bcl-x without perturbing function but not by a somewhat similar region near the N-terminus of Bax. Bcl-2 cell survival activity was reduced by substitutions in two of ten conserved BH4 residues. Deletion of BH4 rendered Bcl-2 (and Bcl-xL) inactive but did not impair either Bcl-2 homodimerization or ability to bind to Bax or five other pro-apoptotic relatives (Bak, Bad, Bik, Bid or Bim). Hence, association with these death agonists is not sufficient to promote cell survival. Significantly, however, Bcl-xL lacking BH4 lost the ability both to bind CED-4 and antagonize its pro-apoptotic activity. These results favour the hypothesis that the BH4 domain of pro-survival Bcl-2 family members allows them to sequester CED-4 relatives and thereby prevent apoptosis.
Huang
D C
DC
The Walter and Eliza Hall Institute of Medical Research, Post Office Royal Melbourne Hospital, Victoria, Australia.
Adams
J M
JM
Cory
S
S
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D000072224:Bcl-2-Like Protein 11; D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D017124:Conserved Sequence; D019281:Dimerization; D015801:Helminth Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
D051017:Apoptosis Regulatory Proteins; C494819:BAD protein, human; C494772:BAK1 protein, human; C494826:BAX protein, human; C494811:BCL2L1 protein, human; C000606775:BCL2L11 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; C096820:BIK protein, human; D000072224:Bcl-2-Like Protein 11; D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; C089224:Ced-4 protein, C elegans; D015801:Helminth Proteins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein